The site(s) of integration of the polyoma virus genome in transformed Syrian hamster cells will be characterized. Cell DNAs from independently transformed hamster cells which are inducible for viral DNA replication, and from uninducible derivatives of these cells, will be digested with site-specific restriction endonucleases and fractionated by agarose gel electrophoresis. The topology of the polyoma genomes relative to the adjoining cell sequences will be examined. The state of the viral genome in the inducible cell lines will be compared with that in the uninducible cell lines.